Fix xmlDecl and docTypeDecl giving wrong value in some cases
Fix xmlDecl and docTypeDecl giving wrong value in some cases

If they are not present in the parsed document, return undefined, not empty
string.

mltframework/swfdec,mltframework/swfdec,freedesktop-unofficial-mirror/swfdec__swfdec,freedesktop-unofficial-mirror/swfdec__swfdec,freedesktop-unofficial-mirror/swfdec__swfdec